Use of Arthrospira platensis in diets for juvenile mullet (Mugil liza )

Author: Victor Torres Rosas (Currículo Lattes)
Supervisor: Dr Marcelo Borges Tesser
Co-supervisor: Dr Luis Alberto Romano

Abstract

The use of alternative ingredients in aquaculture is a field of study of nutrition, where its objectives are the improvement in zootechnical parameters, by stimulating the immune and antioxidant systems of fish. The cyanobacterium Spirulina (= Arthrospira platensis) is recognized for its high protein content (60-70%) and also for the wide benefits it provides to health, which is why it is used in animal and human nutrition. To analyze its use in the feeding of juvenile mullet (Mugil liza), three experiments were planned; 1) five experimental diets were developed to evaluate the partial and total replacement of fishmeal by Spirulina (0, 30, 50, 70 and 100%). The diets were offered for 80 days, when the effect of this inclusion on the non-specific immune system was evaluated.2) Based on the results of the first trial, partial and total replacement of fish flour and oil by Spirulina and flaxseed oil (0, 30, 50, 70 and 100%) was carried out. In addition, lysine was included to improve the protein quality of Spirulina. The experiment lasted 75 days. The effects of this substitution were evaluated on the antioxidant system and the quality of the fillet. 3) The effect of including Spirulina (0, 5 and 10%) was compared against the inclusion of β-carotene (50mg kg-1). The experimental diets were offered for 75 days and, after the experimental period, their effects on the antioxidant system and the quality of the fillet were evaluated. 4) In this last chapter, a review was made on the substitution and inclusion of Spirulina in diets for aquaculture,compiling much of the research in this area and evaluating why the use of Spirulina at the commercial level is not yet a reality. Our first results showed that up to 50% of fishmeal can be replaced with benefits in growth and stimulation for the production of T lymphocytes and in stimulation for apoptosis. The second trial demonstrated that with double substitution and inclusion of lysine, up to 70% of fish meal can be substituted without impairing the growth of the mullet. It was also shown that attributes such as color and carotenoids in the muscle do not provide benefits beyond the 30% inclusion in Spirulina, and that this supplement increases the capabilities of the antioxidant system. Finally, in this expeiramento it was concluded that the mullets accumulate essential fatty acids and that in large part reflect the profile of the diets.In the third experiment it was found that Spirulina and β-carotene bring benefits to the growth and quality of the fillet. Spirulina provides more benefits than β-carotene in the mullet's antioxidant system. Finally, it was evaluated that the production of Spirulina has a high cost when considering the price volatility of fishmeal, so more alternatives are proposed in order to reduce costs in the near future. As a general conclusion of the thesis, we believe that the inclusion of Spirulina in commercial diets could become a reality, since even in a small amount, it adds health benefits to organisms, which in general, protects the production of risks inherent to aquaculture.

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